The term “cloud” or “cloud computing” may refer to a network for providing hosted services over the Internet (or another network) or to providing hosted services by the cloud, respectively. Cloud services are generally tailored to give the illusion of unlimited and ubiquitous resource availability. Services provided by a cloud may include a Software-as-a-Service (SaaS), Platform-as-a-Service (PaaS), and Infrastructure-as-a-Service (IaaS).
SaaS includes providing software application instances via the cloud. Typically, such applications are client-server types, with the server instances running in the cloud and the client instances running on customer devices. Examples of SaaS applications include Microsoft Office 365 and Google Apps.
PaaS includes provisioning platforms needed for deployment of software applications on the cloud (e.g., operating systems, web servers, databases, etc.). Examples of PaaS systems include Amazon Web Services (AWS) Elastic Beanstalk and Google App Engine.
IaaS includes provisioning physical devices or virtual machines, disk spaces, computing power, memory, network devices (e.g., physical and/or virtual routers, etc.). Users may install operating systems, applications, etc. on the provisioned infrastructure. Examples of IaaS systems include Amazon Elastic Compute Cloud (EC2) and Google Compute Engine.